Controller for electric motors



F. E. CASE.

CONTROLLER FOR ELECTRIC MOTORS. APPLICAHON FILED SEN-21,1918.

1,352,247, PatentedSept. 7, 1920.,

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F. E. CASE.

CONTROLLER FOR ELECTRIC MOTORS.

APPLICATION FILED SEPT-21,1918- Patented Sept. 7, 1920.

2 SHEETSSHEET 2.

Inventor: Frank E. Case,

H is T ttorne UNITED STATES PATENT OFFICE.

FRANK E. CASE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

CONTROLLER FOR ELECTRIC MOTORS.

Specification of Letters Patent.

IfltOl'ltQd Sept. 7, 1920.

Application filed September 21, 1918. Serial No. 255,142.

To all QFZLOIU it 7721111, concern:

Be it known that I, FRANK E. CASE, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements in Controllersfor Electric Motors, of which the 'lollowing is a specification.

My invention relates to the control of electric motors and has for itsobject the provision of improved means whereby the motor may be started,stopped and generally controlled in a reliable, simple and eliicientmanner.

My invention relates more specifically to pueun'iaticalhJ operatedcontrollers of the type in which a ste 'i-l'iy-step movement is desired.In the pneumatically operated controllers diliiculty has beenencountered in securing a positive and definite step, there being atendency to overtravel which results in trouble at the controllercontacts. In the usual type of: pneumatic engine, for instance, a pistonis moved forward an increment in a cylinder for each step of thecontroller, and. it is diflicult to insure that the piston shall moveonly the predetermined distance, since owing to the inertia of theparts, there is a decided tendency to overtravel. In order to .overcomethis ditliculty and at the same time provide a pneumatic engine which isvery easily controlled. I employ a multiple cylinder engine, preferablyhaving three cylinders 120 degrees apart. The arrangement such that acomplete stroke of each piston in its cylinder turns a shaft 120degrees, which is equivalent to one step on the controller. When astroke is completed, the pressure is left on the piston and there is notendency for the piston to either go farther or to return. It makes anabsolutely definite stroke and stops. To take-another step, the air mustbe exhausted from the cylinder, since the piston must return freely andat the same time air under pressure must be admitted to the succeedingcylinder. To accomplish each step, therefore, air must be admitted toone cylinder and exhausted from the preceding cylinder.

In one arrangement I provide a valve,

preferably an electromagnetic valve, which is automatically operatedupon each step of the controller to effect the stopping of the engine byleaving the air pressure on' the cylinder which has just been operated,the other cylinders, of course, being disconnected from the air pressuresupply. To take another step, the operator must move his handle tooperate the valve. When the engine is in a stationary position and isconnected to be driven in a forward direction, the operation of thisvalve admits air to the next succeeding cylinder through the agency of amoving distributing valve which admits air under pressure to eachcylinder in succession, and simultaneously with such ad mission exhauststhe preceding cylinder which had been under ressuro. hen the engine isin a stationary position and connected to be driven in a reversedirection, the operation of this valve admits air to the next precedingcylinder through the agency of said distributing valve andsimultaneously exhausts the air from the cylinder just operated.

One of the important features of my improved arrangement lies in thefact that when one piston has completed a stroke to give the controllera step, one of the two remaining pistons will, be in a position to movethe controller another step in the same direction, while the otherpiston is in a position to move it in the opposite direction, so thatafter a step is taken, by admitting air to one of the tree cylinders,the controller will be moved forward, while by admitting air to theother cylinder, the controller will be moved backward. This constitutesa very convenient arrangement for reversing the movement of thecontroller. Other objects and purposes of my invention will appear inthe course of the following specification in which. I have shown myinvention embodied in concrete form for purposes of illustration.

In the accompanying drawings, Figure 1 is an elevation of my pneumaticengine and controller shaft partly in section: Fig. 2 is a sectionalview through the cylinders; Fig. 3 is a section on the line 33 of Fig.1; and F 4- is a diagrammatic view illustrating the operation oi theengine. Figs. and 6 are views of the valve passages.

Referring to the drawings, 1 is a controller shaft driven by mypneumatic engine through crank shaft 2 and gears 23 and 4. The pneumaticengine comprises three cylinders 5, (3 and. 7 mounted around the crankshaft, the center line of the cylinders being radial to the center lineof the shaft, at equal distances from each other, that is, 120 degreesapart. Pistons 8, 9 and 10 fit into the cylinders 5, 6 and 7respectively, and are arranged to drive the crank shaft withstep-hy-step movement, a complete stroke of each piston corresponding toan angular movement of 120 degrees of the crank shaft. Each piston issingle acting, that is, it drives in one direction only and is returnedfreely by the operation of a succeeding piston. linstead of connectingthe crank shaft with the pistons in the usual manner hy a connecting rodournaled on the crank shaft, the crank is free with respect to theconnecting rod, that is, the connecting rod pushes the crank shaftforward but is not attarhed to it. The arrangement is such that when thepiston makes its complete stroke there is no possibility of its goingany farther, as it is mechanically and positively stopped. In thisposition the movement of one of the other pistons will turn the crankshaft in one direction, while the movement of the other piston will turnthe crank shaft in the other direction. Tie partnnlar connection betweenthe pistons and the crank shalt which i. have illustrated comprises atrian- 'ular crank member ll provided with rollers .12 and 12 at two ofthe corners, while the third corner is secured to the crank shaft Thepistons provided with driving heads 1%, l5 and 16, each having anelongated shank l'i' pivoted to igs piston. at 18. These driving headsslide in guides 19 and have flat driving surfaces which engage therollers and 1.3.

llho operation of this arrangement will be clearly nndcrstooil from aconsideration of 2. ln this ligure piston 10 has completed a stroke andthe two rollers 19. and 13 both engage the flat surface of the drivinghear! l-l equal distances on opposite sides of the center line of thepiston. The piston, therefore, has no turning moment whatever upon thecrank shaft. Furthermore, any tendency of the driving head to return wll not transmitted to the crank shaft since the driving head is free ofthe crank. its hereinafter pointed out, there is no tendency of thedriving head to return since, at the e d o a stroke. prez is'sure isleft on the pist n until the pressure is applied to the suci'zcecingpiston. lt will he further noted from Fig. 2- that while the frank l lin a position of equilibrium with r rence to the driving}; head l t,this is not true with reference to driving hads l5 and 16. he roller 12on the crank engages the driving head 15 to the right of the center lineof thrust so that any forward movement of this head will drive thecrank, and hence the crank shaft, in a counter clockwise direction,whereas the roller 13 occupies an opposite position with reference todriving head 16, and hence a forward movement will drive the crank inthe opposite direction. This same relative position of the parts isassumed at the end of each stroke so that by applying pressure to one ofthe two pistons which are in retracted or operative position, the crankwill he turned in one direction, while by supplying pressure to theother it will be turned in the opposite direction.

ln l l-have illustrated diagrammaticall y the valve arrangement wherebythe admission and exhaust of the air to the cylinders is controlled.These valves are normally held in an open position by springs a and Z)respectively. Referring to this drawing it will be seen that l haveprovided two electromagnetic valves, which ll. shall designate as awhole as A and l5 respectively. T have shown these valves onlydiagrammatically in order to illustrate their functionand have notattempted to show their structural arrangement. Each of these valves hastwo positions, one wh'ch it assumes when its winding is energized andthe other when it is deenergized. Valve ll is shown for purposes oflllllf-Ltlllllflll and to 'i acilitate an unoerstanding of the arrangement as a triple valve, that is, there are three movable members 20, 2and 22, one for each cylinder, whereas the valve A is shown as havingonly a single valve member. If the two valves A and B are both in thesame position, air is admitted to a cylinder and 1e crank shaft will berotated, t 1e direction depending upon the position of the valves. lfthey are both in the energized position, the movement will. he forward,whereas if they are both in deei'iergized POSll'iQil the movement willbe reversed. As shown in Fig. 4:, for instance, the valves are both inenergized position and air is admitted to cylinder 7 so as to give aforward or clockwise rotation, but if the valves were both indeenergized position, the cyliiuler G would receive air and thedirection of rotation would be reversed. If, therefore, the two valveswere left in either the energized. or dee'nergized position, the shaftwould con tinue to rotate in either a forward or reverse direction untilit reached a positive stop, whereas if the valve B alone he moved to theopposite position without changing valve A, or if the two valves occupypposite positions, the operation of the engine will he stopped. Thearrangement whihh I. employ, iowever, is such that while valve left inone position, when a movement of the controller through more than onestep is desired, the valve l3 moved to deenergized positionautomatically at each step and is restored by the operator, thereby giving a step-by-step movement to the crank shaft under the control of theoperator.

The arrangement whereby the magnet winding of valve B is controlled ateach step is illustrated in Fig. 4 from which it will be seen that thecircuit of the winding is controlled by switch arm 23, pivoted at 24.This switch arm is normally hcid in closed position by spring 25, and isopened by the rotation of a star wheel 26, having teeth correspondingwith the steps of the controller and rotating therewith. As shown aprojection 27 roller in Fig. 2) engages the teeth of the star-wheel andlifts the switch arm to open the circuit of the magnet B at contacts 28.When it is lifted, however, it is held in raised position by a magnet29, which is energized from the master controller G direct to round. Inorder to take another step, therefore, the magnet 29 must be deenergizedby the op erator so as to permit the spring to force the switch memberto closed position. As each step is made, therefore, the mastercontroller being in position 2, the circuit of the winding of valve B isautomatically opened by the star-wheel and is closed by the operatormoving the master controller back to position 1. thereby deiinergizingmagnet 29 and then'back to position 2 which re energized winding B. Theresult is that the controller takes a step at a time in accordance withthe movements of the master controller by the operator from position 2to position 1 and back.

I shall now describe indetail the arrange ment of the valves and airpassages whereby the result above described is accomplished. Forpurposes of illustration 1 have shown the rotating valve as beingcomposed of an outer ring or passage 30 connected with segmental passage31. These two passa osarc shown'shadcd and receive air from, thereservoir through valve A and onduit 32. There is also an inner ring 33and an outer segmental ring 34 connected to it, which I have shownstippied, this being coni'iected, with the valve A by conduit Valve Abeing in its energized position,

therefore, as shown. in the drawing, the shaded pas ages will receiveair under pressure from the reservoir, whereas if the valve ii is in itsupper or deiinergized position,the

stippled passages will receive air under pressure from the reservoir.hen one passage is connected with the reservoir the other is connectedwith the exhaust. There is also a segmental pa, "a 36 which I have showndotted, and which is connected to the exhaust, for purposes which willhereinafter appear. it will be understood, of

course. that these circular passages fornr part of a sliding valve whichrevolves 120 sage 80 to the inner through the conduit to the valvemember 1-1 p 38 to the cylinder 7. Since both of the other cylinders arenow connected to exhaust, (cylinder (3 through conduit 39, valve member22, conduit 40, through the passage 36 to exhaust 36, and cylinder 5,through conduit 41, valve member 20, conduit 42, passages 34- and C33and conduit the piston 10 will be forced forward rotating the crankshaft in a clockwise direction as shown in.

Fig. 4. The piston 8 of cylinder 5 which has just made a stroke is atthe limit of its movement and is, therefore, forced haikward and thepiston 9 of cylinder 6 is near i s inimrd-limit and is forced backslightly. :\s the piston 10 movs forward its full stroke, the shaft willbe rotated in a manner heretofore described. As the shaft moves forwardthe magnet winding B is dci nergizcd at the contacts 28 and the valvemoves to its opposite position, the result of which is to intert-u 'itthe passage from th conduit 37 to conduit 38 and open conduit 38 whichis now in engagement with passage l to conduit 38, thus maintaining airthe valve member 22. If now the operator desires to move another step,he moves the master controller back to position i to deenergize thewinding 29v and. then back to position 2 so that the circuit of thewinding of valve B will be again completed, thereby leaving the valvesA. and 13 once more in energized position. The passage isnow open fromconduit 40to cylinder 6 so that the piston 9 moves forward and at thesame time cylinder 7. is exhausted through the conduit 37 which is nowin en gagement with passage so that the exhaust takes place throughconduit The result is that the controller moves forward another step. Inthe same way by moving the master controller to position 1 and back toposition 2, the air pressure will. be admitted to cylinder 5 throughconduit 42, which upon the second stepwill be in engagement tinuouslyforward the operator wishes to reverse. Assume that the parts are in theposition shown in Fig. 4, that is, a stroke has just been completed bythe piston 8, but the Winding of the valve B has not yet been energizedby moving the master controller from position 1 to position 2 and hencethe valve is in its upper position. 1n other words, the operator has notyet moved the master controller to energize the valve 13 to move forwardbut instead deenergizes the winding of valve A by master controller tooff position to go backward. The valves A and B will now both be in thedeenergiaed position which is the opposite to that shown .in the drawingso that the air pressure instead of being admitted to cylinder? will beadmitted to cylinder 6 through conduit 85, passage33, passage 34,conduit 43, valve member 22 and conduit This will drive the shaft in acounter clockwise direction step by step and will continue to operateantomati ally in, that way if the operator keeps the master controllerin the off position stop, the master controller is moved to position 1and to restore the forward movement the master controller is moved toposition 2. In this way the controller will be moved forward one step ata time in either direction at the will of the operator.

As above pointed. out, the rotation of the circular passages in Fig. 4is purely diagrammatic and illustrative, since it does not rep resentthe actual. construction of the sliding valve. The mechanicalconstruction of this valve arrangement is indicated in Figs. 1, 5 and 6from which it will be seen that the member 44 which corresponds with themoving member in Fig. L is driven by a shaft 45 which is an extension ofthe crank shaft and forced toward its cooperating valve member 46 by aspring 47. These two parts of the valve, the stationary part and themoving part, having their ports and passages as indicated in Figs. 5 and(5 constitute the sliding valve arrangement shown diametrically in Fig.4-. I have indicated as far as possible the ports and passages in Figs.5 and 6 with the same numerals as are used in Fig. 4. It is, therefore,unnecessary to go into further detail regarding the Valve arrangement.

In Fig. 3 I have shown some of the details of the valves. Air isadmitted to the air chest 48 through the pipe 49, from which it isdistributed by valves A and B; hen the windings of the valve A areenergized, air passes through the passage 50 into passage 51 and thenceto the diaphragm 52 forming part of the plunger 53. Secured to thisplunger is a valve member 55 which corresponds with the sliding memberof valve A, Fig. 4. lvllen the windings are deenergized exhaust takesplace through the exhaust passage 56. In like manner the energizeisaaaavtion of the winding of valve B moves the valve member 57 whichcorresponds with the three moving members 20, 21 and 22 in Fig. 4.

It will be seen that I have provided a pneumatically operated controllerin which a positive step by step movement is brought about under thecontrol of the operator, the arrangement being such that there is nopossibility of over travel, while at the same time being very effectiveand simple.

ll hile l. have described my invention as cn'ibodied in concrete formand as operating in a specific manner in accordance with the provisionsof the patent statutes, it should be understood that I do not limit myinvention thereto, since various modifications thereof will suggestthemselves to those skilled in the art without departing from the spiritof my invention, the scope of whic i is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. In a circuit coi'itroller the combination with a controlling member,of means for operating the same comprising a plurality of pistons, meansfor applying fluid pressure to said pistons successively and connectionsbetween the pistons and the controlling member whereby a complete strokeof each piston advances the controlling member a step and returnsanother piston to operative position.

2. in a circuit controller the combination with a controlling member, ofmeans for operating the same comprising a plurality of pistons, meansfor applying fluid pressure to said pistons successively and connectionsbetween the pistons and the controlling member whereby a complete strokeof each piston advances the controller a step and places the otherpiston in position to operate the controlling member when pressure isapplied.

3. In a circuit controller the combination vith a controlling member, ofmeans for operating the same comprising a plurality of pistons, meansfor applying fluid pressure to said pistons successively and connectionsbetween the pistons and the controlling member whereby a complete strokeof each piston advances the controller a step and places two otherpistons in position to operate the controlling member in oppositedirections when pressure is applied. 7

4i. In a circuit controller the combination with a controlling member, acrank for driving the same, three pistons acting on the said crank eachof which turns the crank 120 degrees and means for applying fluidpressure to one of said pistons at a time.

5. In a circuit controller the combination with a controlling member, acrank for driving the same, three pistons radially disposed fluidpressure to one of said with respect to the crank at angles of 120degrees from each other acting on the said crank each of which turns thecrank through a definite angle and means for applying pistons at a time.

G. In a circuit controller the combination with a controlling member acrank for driving the same, three pistons radially dis posed withrespect to the crank at angles of 120 degrees from each other acting onthe said crank each of which turns the crank through a definite angleand means for applying fluid pressure to one of said pistons at a timeand leaving the pressure until the pressure is applied 'to anotherpiston.

In Witness whereof, I have hereunto set my hand this 20th day of Sept,1918.

FRANK E. CASE.

